Searching for the Origins of the First Americans

A land bridge between Siberia and Alaska that now lies underwater holds vital clues to the story of the Americas’ first inhabitants. A new project bringing together archaeology, genetics, and molecular biology may rewrite the history books.

Since the 1920s, scientists have debated whether the first Americans arrived from Asia—or somewhere else—some 11,000 years ago, or millennia before. Artifacts such as this Clovis spear point have provided some clues, but new multidisciplinary research is filling in the picture.Eric Albrecht, The Columbus Dispatch/Associated Press

Nearly 30 years ago, I published a book about the first Americans called The Great Journey. At the time of my research, I found myself immersed in an academic world of sharp controversy and diametrically opposed hypotheses. Personality conflicts pitted expert against expert: Passionate advocates for Clovis—the prehistoric, Paleoindian culture that lived roughly 11,000 years ago in present-day New Mexico and elsewhere—were on one side, and those who believed in a much earlier, pre-Clovis date for first settlement, even as early as 40,000 years ago, were on the other. I was astonished by expectations that I would take sides in a controversy that had endured in one form or another since the 1920s. In the end, I carefully navigated these perilous academic shoals and gladly moved on. Since then, my interest in the subject has been somewhat tangential—until, that is, new findings about the Bering Land Bridge came along.

In recent years, the first-Americans debate has focused on pre-Clovis evidence for human settlement. Fortunately, the academic temperature has cooled somewhat. A new generation of long-term, multidisciplinary research is slowly replacing the often far-from-rigorous fieldwork of yesteryear, and paying rich dividends.

Now researchers are putting their weight behind an exciting and provocative scenario for the first settlement of the Bering Land Bridge between Siberia and Alaska. The Beringian standstill hypothesis is based on years of highly specialized, fine-grained research by scholars from many disciplines and from both sides of the Bering Strait and further afield.

The Beringian standstill hypothesis suggests that during the last glacial maximum people lived on the Bering Land Bridge. As of approximately 12,000 years ago, most of the bridge had disappeared under seas that rose as temperatures warmed.NOAA/Wikimedia Commons

The name Beringia was originally used by Swedish botanist Erik Hultén to mean the land that lies beneath the shallow waters of the Bering Strait. In 1937, he pointed out that approximately 20,000 years ago, when global sea levels were hundreds of feet below today’s levels, Siberia and Alaska were joined by a land bridge dissected by meandering rivers. About 12,000 years ago, after the oceans rose as post–ice age temperatures warmed, the land bridge mostly vanished. Beringia in the strict sense ceased to exist.

A handful of scholars still believe that the first settlers crossed oceans to arrive in the Americas. Some theorize that late ice age hunter-gatherers from Western Europe traveled by canoe along northern coastlines and ice sheets to North America. Other outlying theories hold that the first Americans crossed from Japan or some other part of Asia, or even Polynesia. There is scant evidence, however, to support any transoceanic theory. Almost every scientist agrees that the primordial Native Americans arrived from Siberia. In recent years, both molecular biology and dental research have confirmed this Siberian ancestry.

But what was life like for these people? For years, I and many others have painted a portrait of tiny bands of big-game hunters from Northeast Asia who walked on dry land from Siberia to Alaska before rising sea levels severed the land bridge. The portrait is compelling and has been the subject of several book covers. Early deep-sea core borings and fossil pollen studies showed that the backdrop was an intensely cold, windy, and treeless place covered with low scrub. Although not a hospitable landscape, it had one advantage—a sparse population of large ice age mammals, including the long-haired mammoth. Inevitably, artistic depictions of skin-clad hunters attacking long-tusked beasts informed a popular motif. Many of us assumed that the Beringians were big-game hunters and little else. But we were wrong.

What was the Bering Land Bridge really like? This is where the new interdisciplinary research comes into play. Collaborative inquiries led by archaeologist John Hoffecker, geneticist Dennis O’Rourke, biologist Scott Elias, and many others have looked closely at the very sparse archaeological finds on both sides of the Bering Strait, as well as the landscape and the molecular biology of Beringia. Earlier this year, a National Science Foundation workshop in Boulder, Colorado, brought together 25 scholars for intensive discussions on Beringia and the first Americans.

What do we know for sure? Let’s start with the landscape. Thanks to pollen samples, deep-sea cores, and other lines of evidence, we know that around 30,000 years ago Northeast Asia was a relatively comfortable setting for hunting and gathering peoples. This vast region offered a variety of large mammals and smaller game for food, and at least a modest amount of wood for fuel. We also know, thanks to the research of Russian archaeologist Vladimir Pitulko and his colleagues, that Beringia itself was already inhabited at this time.

The sea level in the Bering Strait today is hundreds of feet higher than it was when the Bering Land Bridge connected Siberia and Alaska.Public Domain Images

Pitulko’s team has excavated a remarkable group of 32,000-year-old sites near the mouth of the Yana River in what would have been the northwestern portion of Beringia. (Beringia is now more broadly defined as the region stretching from the Verkhoyansk Mountains in the west to the Mackenzie River in the east.) At the workshop, these sites were described as the “Olduvai Gorge of Beringia”—a reference to the famous fossil site in East Africa that has reshaped our understanding of human origins—because they yield a wealth of archaeological and environmental information about life in Beringia during the ice age.

Around 30,000 years ago, climates in Northern Asia became extremely cold and dry, and there is evidence for a large-scale abandonment of much of the region. Plant productivity declined with the cold, which had an immediate impact on the animal population. Think of Arctic deserts as sets of lungs. In warmer and moister times they breathe in people and animals, then they exhale them when aridity and cold intensify. This is what happened in Siberia during the last glacial maximum—the period of maximum cold during the last ice age, from roughly 30,000 to 15,000 years ago. (At the same time, people in other parts of the world such as Western Europe and Africa also retreated into environmental refuges in the face of either cold or drought—or both.)

The plot thickens on the land bridge in the low-lying center of Beringia. Could it have supported human life during the height of the last ice age, and if so, was it the only place that did? We now know a great deal more about the landscape there thanks to deep-sea cores and research on islands in the modern-day strait. These cores, with their diatoms, minute shells, and pollen, reveal a mosaic of cold landscapes significantly different from the harsh terrain of Siberia. Here, shrub tundra and occasional trees mantled the dry and windy landscape. Elias’ studies of beetle remains found in the cores show that even at the height of the last glacial maximum temperatures in the Bering Strait region were about the same as they are today. This occurred because of the benign influence of North Pacific currents that brought warmer and wetter conditions to the land bridge.

The new scenario for the first Americans assumes that the land bridge was a refuge for animals, plants, and humans—including the immediate ancestors of the first Americans—during the peak of the most recent glacial period. What, then, do we know about human actors across these diverse Beringian landscapes? Genetics are a starting point.

All Native Americans stemmed from a single group that later diversified into two branches.

The split between Siberians and Native Americans may have occurred about 23,000 years ago—the chronology is approximate. Genetic information from modern populations as well as from a handful of ancient skeletons confirms that all Native Americans stemmed from a single group that later diversified into two branches: one that included Amerindians, who occupied North America south of the ice sheets and also Central and South America, and one that included Athapaskans, Paleo-Eskimos, and Inuit in the far north. Geneticists believe that the split into northern and southern branches took place about 13,000 years ago. At some point between these two splits (between 23,000 and 13,000 years ago), people on the land bridge moved into Alaska.

This, then, is the Beringian standstill hypothesis: a pause in human migration between about 30,000 and 15,000 years ago (during the last glacial maximum) that set the stage for the first settlement of Alaska when temperatures warmed.

Central Beringia likely supported life, then—but it probably wasn’t the only place on the land bridge that did. The most dramatic revelation of the Boulder workshop was Pitulko’s report that new radiocarbon dates on ivory artifacts from one of the Yana River sites fall in the midst of the last glacial maximum (about 21,000 years ago). If confirmed by future research, the new dates from the Olduvai Gorge of Beringia suggest that the refugium extended far beyond the central land bridge and that people were living, or at least periodically visiting, other parts of Beringia during this time period.

As temperatures warmed across Beringia beginning around 18,000 years ago, very small numbers of people pushed into Northeastern Siberia and onto the land bridge. Perhaps they encountered the descendants of the Beringian standstill population, also on the move. They brought with them a stone technology from Siberia, Mongolia, or even Japan that was ideal for hunters traveling in very cold environments. Their barbed hunting weapons were comprised of small, very sharp “microblades” knocked off from lumps of fine-grained rocks. They also hunted with spears tipped with nicely flaked stone projectile points. Fortunately for archaeologists, we can trace the distribution of these distinctive technologies over very long distances. Both the edge-shaped blanks used to make microblades and small, teardrop-shaped spear points appear in Alaska as early as 14,000 years ago.

With the possible exception of the new finds from the Yana River sites, we know nothing about the archaeology of the people who lived in the Beringian refugium during the last glacial maximum. They were genetically diverse, and perhaps as many as 6,000 to 10,000 people inhabited the area. As temperatures warmed and the land bridge began to flood with the rising seas, they apparently moved into both Alaska and Northeast Asia. Some of the archaeological remains found in Northeast Asia and Alaska over the past 50 years might have been made by the descendants of these people.

Human-made stone landmarks, or cairns, mark routes as well as areas where hunters sought caribou, providing rough dates for when humans moved out of Beringia to higher ground in Alaska.Bering Land Bridge National Preserve/Wikimedia Commons

Just when people moved onto higher ground in Alaska is unknown. That move seems to have occurred at a time when mean summer temperatures were rising over much of Beringia, around 15,000 years ago. We know this from Elias’ fossil beetles, which are sensitive to temperature change, and also from pollen records that chronicle a shift from primarily shrub tundra to shrub tundra mixed with trees like birch and poplar, which signals an increase in overall moisture. Many of the large animals hunted during the last glacial maximum became extinct, which meant that the Beringians, including the first Alaskans, were broad-spectrum hunters whose diet included everything from caribou to small mammals, fish, and birds.

At least some of these early Alaskans eventually migrated southward into more temperate zones, but their archaeological signature is faint. For example, stemmed points at sites like Arlington Springs on Southern California’s Channel Islands may be a credible link to Beringia. Mitochondrial DNA from a 12,600-year-old infant burial at the Anzick site in Montana may also hint that the Clovis tradition was developed by people from the Pacific coast.

Much of the standstill hypothesis depends on genetics, which is still somewhat in a state of scientific flux. Those working on the hypothesis readily accept that there will be major changes in the future. But these scholars offer a plausible scenario for first settlement that is based not on wild claims but rather on meticulous and imaginative multidisciplinary research. And that’s the future of research into the first settlement of the Americas.

This is terrific stuff and very persuasive. What the scientists are missing — thus the author’s puzzlement at the controversy — is that the Bering Strait theory is often used to justify the invasion by the Euros across the Atlantic. Ignoring the time scale, the people who use this rationale say that the indigenous Americans have no business feeling invaded when they did the same thing from the other ocean. It’s a dumb argument but it’s persistent because of the emotional appeal.

Jeff Lewin

I have been open in discussing difficulties with the Solutrean hypothesis concerning chronology, geography, paleoclimate, and paleo-oceanography in various forums. On the other hand, given Dr. Dennis Stanford’s convincing evidence of a maritime culture in pleistocene Western Europe; the well-known submersion of all coastal sites on both sides of the Atlantic; and the general paucity of archaeological evidence and human remains for the relevant timeframe, at this stage, to either categorically rule out travel across the Atlantic, or to draw hard conclusions, is overly presumptuous. The blatant audacity of academics sniping at Dr. Stanford & et. al. begs the question of what is motivating them.

peterjohn936

While there is no evidence for the first people reaching America did so using canoes there is also no evidence that they reach America by crossing the land bridge. The consensus theory also needs to be as rigorously proven as any other theory.

Jeff Lewin

The N. American ice sheets only merged, c. 21 kya. Conventional archaeology keeps getting stumped trying to explain discoveries of paleoindian sites earlier than the ice free overland passage that opened 13kya (according to the most recent research); or how whole family groups could have navigated 1,500 miles of glaciated coasts from around Anchorage to Washington State before 14.5 kya. Why not consider whether paleoindians migrated to the inner continent before 21 kya, before the ice sheets merged?

Helga Vierich

The coastal and riverine routes have some implications for the dating of the colonization of the Americas that Fagan has not really explored here. Yet, the possibility of a coastal route has been considered for long time. Such a route might have resulted in a much earlier penetration of the coastal zone along the western North American coast. this could possibly have happened as early as 40,000 BC, just on the basis of calculations of simple demographic expansion, especially if there is evidence of Homo sapiens in southern China and India by 100,000 BC. Certainly there is evidence of occupations and ceremonial sites off the Western American coast.

If humans with a coastal hunter-gatherer economy were expanding along a coastal route, with a modest rate of .05% increase in population per year, they might have reached coast regions of South America and advanced inland as early as 30,000 years ago. This would actually also accord with the finding, reported by Fagan here, that the DNA evidence from North and South American populations indicates a single origin. There is evidence that this population split into two branches early on, and that one branch are descendent of those whose easiest entry was achieved along a coastal route, but the suggested dates for the timing of this split are estimates that may be conservative and influenced by the currently accepted timing of peopling of the the Americas.

Also, consider this:

“From our findings, it follows that an ice-free corridor was unavailable to those groups who appear to have arrived in the Americas south of the continental ice sheets by 14.7 cal. kyr bp6,7, and also opened too late to have served as an entry route for the ancestors of Clovis who were present by 13.4 cal. kyr bp1,9…. More striking, once opened, the corridor was not used just for southbound movement: archaeological evidence suggests that people were moving north as well, potentially renewing contact between groups that had been separated for millennia1,9. Bison3 were also colonizing the corridor and moving north and south; it is uncertain whether other species, such elk2 and brown bears48, were moving similarly.” http://www.nature.com/nature/journal/vaop/ncurrent/full/nature19085.html

Elizabeth Neily

Politicians know that if you say the same thing over and over again, people will eventually believe it. Apparently Brain Fagan and a lot of American archaeologists feel the same way. Their wild claims of a 12,600 year old date just makes no sense at all. In truth, science is really driven by politics and money. Any site or research which doesn’t line up with the “accepted theory” loses its funding and gets shouted down.

Where does the most evidence of Clovis culture come from? Alabama and Florida. I know of 6 Clovis artifacts being found in the Pinellas County region of Florida alone. Clovis projectile points have been found all around the Tampa Bay area, and no one was really looking for them. If we were to go by the overwhelming evidence of artifacts, Alabama would be the obvious center of the Clovis culture. Wow, what would that mean?

Recently, archaeologists excavating the Aucilla River, just south of Tallahassee, came up with a date of 14,500 years old for pre-Clovis evidence. Did the ancient people rush over from Alaska as fast as they could to that site, just to throw around some evidence? Archaeology is not where the largest amount of research money goes. Most work is literally a battle to squeeze every penny’s worth of information out of a site and most sites are never really fully investigated or even recognized at all. There’s just not enough money for that. The wealth and status of your State also figures heavily in the publicized status of a theory. Why of course California would be the birthplace of the First American culture. . . Hollywood could have told us that.

The North American continent takes a big geological bite out of Western Asia/Siberia. The Yana River site should make it very apparent that early humans were in North America at least 32,000 years ago. If they entered Alaska, they just couldn’t go any further. But, Alaska is part of North America, isn’t it? Blocked by the joining of two massive glacial fields, they were stuck and later when when the glaciers melted, humans were faced with all that melt-water. Lake Agassiz was huge.

Good science should not be driven by politics but a passionate curiosity and well considered evidence from the perspective of every possible discipline. Wild theories are the product of politics and poorly publicized information. Too often the public, those who really pay the bill, are left out of the loop.

Before we decided on the definitive answer for Native American arrival in North America, perhaps we should consider, how did the first Australians get to that continent some time between 50,000 to 40,000 thousand years ago?